Conventionally, a polymer electrolyte fuel cell is made up of a cell, two separators disposed on both sides of this cell so as to interpose the cell therebetween, and diffusion layers disposed between the aforesaid cell and the separators.
The aforesaid cell consists of a solid polymer film and two reaction layers disposed on both sides of the film. Each of the aforesaid diffusion layers consists of carbon paper and a slurry layer formed on one major surface thereof. A groove for the passage of hydrogen gas is formed in the surface of one separator facing the cell, and a groove for the passage of air is formed in the other separator.
However, conventional separators for use in polymer electrolyte fuel cells have a problem in that the fuel gas and the oxidant gas do not flow in conformity with the shape of the groove but bypass it by flowing through the aforesaid diffusion layers, so that water is retained in the cell to cause a corresponding reduction in reaction area, a deterioration in electricity generation performance, and a risk of damage to the cell.
Meanwhile, in order to remove the water retained in the cell, there has been employed a method in which the pressure loss in the separators is sufficiently increased to introduce the retained water into the gases as water vapor. However, this method is advantageous in that the gas pressure losses in the polymer electrolyte fuel cell are increased to cause an increase in power consumption by auxiliary devices such as compressors for feeding the gases, resulting in a reduction in electricity generation efficiency of the whole fuel cell system.